1. Field of the Invention
The present invention relates to a data transmission system, and more particularly to a data transmission system which transports data in parallel form.
2. Description of the Related Art
Increasingly large amounts of data have to be transferred and processed at higher speeds in today's computer systems including distributed computing environments. This is also true in communications systems. To meet the demands for greater bandwidths, many systems employ parallel data transfer methods, which use a plurality of signal lines simultaneously to transport information.
In parallel data transmission systems, the difference of propagation delay times between data bits is one of the major factors that determine the performance. This is known as the “skews.” Since the presence of large skews makes it difficult to process incoming data signals correctly, the receivers are required to have a timing adjustment mechanism of some kind. Conventional systems thus employ delay circuits to compensate for data skews, so that all the parallel data bits will be aligned properly.
High-speed digital systems of today, however, must be able to handle signals that change their states in an extremely short time. Even a small variation in a signal's rise time and fall time would have a serious impact on the system's operation, as the transmission rate becomes higher and higher. That is, a slight irregular behavior of signal skews could cause serious adverse effects to data setup/hold time conditions of registers at the receiving end, leading to performance degradation of the system. The above-mentioned simple delay circuits used in conventional systems are not effective enough to correct such skews completely, and accordingly, there is an increasing demand for techniques that avoid transmission losses due to skew variations.